【力扣】47. 全排列 II

给定一个可包含重复数字的序列 nums ，按任意顺序 返回所有不重复的全排列。

示例 1：

输入：nums = [1,1,2]
输出：
[[1,1,2],
 [1,2,1],
 [2,1,1]]

示例 2：

输入：nums = [1,2,3]
输出：[[1,2,3],[1,3,2],[2,1,3],[2,3,1],[3,1,2],[3,2,1]]

提示：

• 1 <= nums.length <= 8
• -10 <= nums[i] <= 10

题解：

回溯法：

func permuteUnique(nums []int) [][]int {
	var path []int
	var result [][]int
	var backtracking func(nums []int)
	var used = make(map[int]bool, len(nums))
	backtracking = func(nums []int) {
		if len(nums) == len(path) {
			tmp := make([]int, len(path))
			copy(tmp, path)
			result = append(result, tmp)
			return
		}
		for i := 0; i < len(nums); i++ {
			if i > 0 && nums[i] == nums[i-1] && !used[i-1] {
				continue
			}
			if used[i] {
				continue
			}
			used[i] = true
			path = append(path, nums[i])
			backtracking(nums)
			used[i] = false
			path = path[:len(path)-1]
		}
	}
	sort.Ints(nums)
	backtracking(nums)
	return result
}